Heating pouch

ABSTRACT

Provided is a heating pouch that can be heated in hot water and in a microwave. That is, the heating pouch includes a bag sheet provided with an easy peel pressure releasing seal part. In the pressure releasing seal part, one part of a sheet constituting the bag sheet and another part thereof are adhered so as to overlap each other. The pressure releasing seal part peels off when internal pressure rises, to form a degassing passage that communicates between an inside and an outside of the bag sheet. The pressure releasing seal part is provided with an easy peel layer and a skin layer. The skin layer is a resin layer constituting a seal surface that coats at least one of the one part and the other part of the sheet and which adheres to the other part which is not coated. The skin layer has a higher seal strength at 100 degrees centigrade than the easy peel layer.

TECHNICAL FIELD

The present invention relates to a heating pouch.

Currently, there are a number of packaging modes with which a food product is heated while in a container bag. In particular, microwave heating a pouch indicated in Patent Documents 1 and 2 is a safe, useful, and hygienic package that can be heated and cooked in a microwave with completely sealed package.

The most remarkable characteristics of the heating pouch for microwave of Patent Documents 1 and 2 are unique automatic vapor mechanisms.

In this heating pouch for microwave, a bag is inflated by steam coming from a heated food product. When the pressure reaches a fixed pressure inside the bag, steam is safely discharged from a steam port thereof to the outside of the bag, so that the food product can be evenly heated. This steam port includes a safety structure, and there is no such danger that the pouch bursts and contents scatter, etc. Further, even when the contents are liquid, the contents are in no danger of leaking out. Thus, the heating pouch is utilized for many cooked food products irrespective of contents thereof.

Specifically, Patent Document 1 shows the following packaging body for heat processing. That is, the packaging body for heat processing includes a first connecting part whose identical surface sides are abutted with each other by plastic films and bonded in a butt-seam shape by a heat seal having a predetermined width, and contents to be subjected to heat process are sealed and packaged inside, wherein the first connecting part is an easily openable seal positioned on the upper surface side of the packaging body at the time of heat processing of the contents, and provided closer to one side part from one end part of the packaging body to the center side, the seal relieving the pressure when an internal pressure of the packaging body is increased by heating.

In particular, a peeling off strength of this easily openable seal is 150 to 1,800 g/15 mm. When the packaging body is inflated, the short side across the first connecting part is brought into a substantially standing state by tensile force due to the inflation, and by tensile force of the film of the packaging body on the opposite long side, the first connecting part rises with respect to an upper surface of the packaging body, so that abutment or adjacency between one side surface of the first connecting part and a short side surface of the packaging body is avoided.

In the packaging body formed in a butt-seam shaped bag, the first connecting part which is formed in a butt-seam has an easily openable property as described above. Further, as described above, in the packaging body, the first connecting part is formed closer to one side part, and after the contents are charged inside, an upper part is sealed and packaged by the heat seal, and then the packaging body for heat processing suitable for preservation and management is completed.

When the contents housed in the packaging body are subjected to heat processing, the packaging body is housed in a microwave and subjected to heating at a predetermined temperature for a predetermined period of time. When the internal pressure is increased by generation of water vapor and thermal expansion of air in the packaging body following the heating, a pressure release part provided in the first connecting part is peeled off and an inside gas is discharged. Thereby, the pressure in the packaging body is lowered. The first connecting part is attached more closely to one side in the packaging body. Thus, when the packaging body is inflated, the short side across the first connecting part is brought into a substantially standing state by the tensile force due to the inflation, and by the tensile force of the film of the packaging body on the opposite long side, the first connecting part rises with respect to the upper surface of the packaging body, so that abutment or adjacency between one side surface of the first connecting part and the surface of the packaging body is avoided. Since a through hole of the pressure release part is positioned in the upper part of the packaging body, no contents are leaked out from the through hole.

Therefore, the excessive pressure increased in the packaging body acts on and peels off a proper part of the first connecting part having an easily openable property, so that the internal pressure is relieved.

Patent Document 2 shows a packaging body for heat processing in which the identical surface sides are abutted with each other by plastic films and formed in a bag by heat seals, a butt-seam shaped steam releasing and connecting part is provided at one point of the heat seals, and contents to be subjected to heat processing are sealed and packaged inside the bag, wherein in the steam releasing and connecting part, a high temperature dependent film is placed between the plastic films, the steam releasing and connecting part is an easily openable seal positioned on the upper surface side of the packaging body at the time of heat processing of the contents, the seal relieving the pressure when the internal pressure of the packaging body is increased by heating, this easily openable seal has peeling force at a normal mode of 3 kgf/15 mm or more and peeling force at the time of heat of 90° C. of 0 to 1,200 g/15 mm, the high temperature dependent film in the steam releasing and connecting part is a tape to be inserted between the plastic films, this tape is a coextruded film consisting of random copolymer polypropylene resin, and a blend which contains 60 weight % of random copolymer polypropylene resin, 20 weight % of ethylene-α olefin copolymer resin, and 20 weight % of metallocene linear low-density polyethylene, or a coextruded film consisting of random copolymer polypropylene resin, and a blend which contains 60 weight % of random copolymer polypropylene resin, 20 weight % of propylene-α olefin copolymer resin, and 20 weight % of metallocene linear low-density polyethylene, and the butt-seam shaped steam relieving and connecting part is subjected to heat sealing via the tape.

In the packaging body in which a food product, etc., is charged with the above configuration, the contents such as the food product can be heated and cooked by a microwave while the contents are packaged, and break-off of the packaging body due to the internal pressure increased by heating can be prevented. In particular, in addition to the simple configuration of the packaging body, unique effects can be exerted, for example, in bag manufacturing or contents charging sealing packaging, manufacturing costs can be reduced and thus packaged food products, etc., can be provided to market at low price.

PRIOR ART Patent Document Patent Document 1: Japanese Patent No. 3035484 Patent Document 2: Japanese Patent No. 4150513 SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The inventor of the present application did not satisfy the above heating pouches for microwave but further actively conducted research, and is intended to provide a heating pouch suitable for both microwave heating and heating in hot water.

Means for Solve the Problems

The present invention provides a heating pouch which is a bag sheet provided with an easily peelable seal part as a pressure release seal part, wherein the pressure release seal part adheres a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other, the pressure release seal part is peeled off at the time of an internal pressure rise so as to form a deaeration passage which communicates between the inside of the bag sheet and the outside of the bag sheet.

The pressure release seal part in the present invention is provided with an easily peelable layer and a skin layer, the skin layer is a resin layer constituting a seal surface that covers at least any one of the part of the sheet and the other part and which adheres to the remaining uncovered part. This skin layer uses a material whose interlayer strength with the easily peelable layer decreases under high temperature in the interlayer peeling type in which the tensile yield stress is higher than that of the easily peelable layer under the high temperature, in particular, the seal strength at 100 degrees is higher than the easily peelable layer. The description “a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other” includes a situation that the sheets are placed over one another so as to directly contact with each other as well as includes a situation that the sheets are placed over one another indirectly via other inclusions, and further, for example, includes a situation that a tape formed on other sheet different from both the sheets is sandwiched between both the sheets and both the sheets are overlapped.

Further, the description “the skin layer being a resin layer constituting a seal surface that covers at least any one of the part of the sheet” includes a situation that the skin layer is directly contact with any of the sheets and covers the sheet as well as includes a situation that the skin layer indirectly covers any of the sheets via other inclusions, and further, for example, includes a situation that the skin layer is provided on a surface of a tape formed on other sheet different from both the sheets and indirectly covers any one of the sheets via the tape. In a case that the tape is to interpose, the skin layers are provided on both surfaces of the tape, and regarding arrangement of the tape to be interposed between both the sheets, for example, the skin layer on the front side of the surface of the tape indirectly covers one of the sheets with the tape and the skin layer on the back surface side as inclusions, and the skin layer on the back side of surface of the tape indirectly covers the other sheet with the tape and the skin layer on the front surface side as inclusions.

The present invention is to provide a heating pouch which is a bag sheet provided with an easily peelable seal part as a pressure release seal part, wherein the pressure release seal part adheres a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other, the pressure release seal part being peeled off at the time of an internal pressure rise so as to form a deaeration passage which communicates between the inside of the bag sheet and the outside of the bag sheet, and the pressure release seal part is provided with a flat part and a bead part, the flat part serving as a flat seal surface and the bead part being formed as projecting toward the inner surface side of the bag sheet rather than the flat part.

The present invention is able to provide the heating pouch wherein the heating pouch is used for both microwave heating and heating in hot water.

Further, the present invention is to provide a heating pouch which is a bag sheet provided with an easily peelable seal part as a pressure release seal part, wherein the pressure release seal part adheres a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other, the pressure release seal part is peeled off at the time of an internal pressure rise so as to form a deaeration passage which communicates between the inside of the bag sheet and the outside of the bag sheet, the pressure release seal part is provided with at least any one of a first seal mechanism and a second seal mechanism, the pressure release seal part has a pressure resistance strength 6 to 30 kPa at 100° C., wherein

the heating pouch is capable of heating in hot water and by the microwave.

In the first seal mechanism, the pressure release seal part is a resin layer constituting a seal surface that covers at least any one of the part of the sheet and the other part which adheres to the remaining uncovered part.

In the second seal mechanism, the pressure release seal is provided with a flat part and a bead part, the flat part serving as a flat seal surface and the bead part is formed as projecting toward the inner surface side of the bag sheet rather than the flat part, the bead part has a pressure resistance strength 6 to 30 kPa at 100° C., the bead part has higher pressure resistance strength than that of the flat part.

The description “heating in hot water” includes both heating in hot water for cooking and heating in hot water for sterilization (boiling sterilization).

In the present invention, the heating pouch can be implemented in such a manner that the pressure release seal part includes an easily peelable tape, and at a temperature higher than a normal temperature, the easily peelable tape is more easily peelable than at the normal temperature.

The present invention can be conducted in such a manner that the pressure release seal part is provided with an easily peelable tape, the easily peelable tape being more easily peelable at a temperature higher than a room temperature than being peelable at a room temperature.

By the above specific means, the present invention provides the heating pouch which is a bag sheet provided with an easily peelable seal part as a pressure release seal part, wherein the pressure release seal part adheres a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other, the pressure release seal part being peeled off at the time of an internal pressure rise so as to form a deaeration passage which communicates between the inside of the bag sheet and the outside of the bag sheet, the heating pouch provides the following means with respect to the pressure release seal part.

As a first means, the pressure release seal part has a pressure resistance strength 6 to 30 kPa at 100° C.

As a second means, the pressure release seal part has a seal strength 1.3 to 20 N/15 mm at 100° C.

As a third means, in the above second means, the pressure release seal part has an initial peak value/intermediate value of the seal strength 1.3 to 3.0 at 100° C.

The pressure release seal part may include the above first and second means respectively separately, or may include the both means together. Alternatively, the pressure release seal part may include all the above first to third means.

The present invention is able to provide the heating pouch wherein the skin layer is to be 3 to 40 μm thick.

In the present invention, by the above each means, in the microwave heating, by peeling off at the time of the internal pressure increase so as to securely form the deaeration passage, water vapor and the like can be released from the deaeration passage, thus bursting due to the internal pressure increase in the bag can be suppressed. Together with this, upon heating in hot water, under a condition of heating in hot water (under a heating condition of about 100° C.), the pressure release seal part is not easily peeled off by the internal pressure increase, a sealed state of the bag can be maintained without forming a deaeration passage, thus, the occurrence of undesirable condition such as the contents flowing out into hot water can be suppressed.

Effects of the Invention

By employing the above configuration, the present invention is able to easily provide the heating pouch suitable for combination use of microwave heating and heating in hot water.

That is, the present invention is able to easily provide the heating pouch with which in microwave heating, bursting due to the internal pressure increase is prevented by peeling off at the time of increasing internal pressure so as to securely form the deaeration passage, and in heating in hot water, the peeling off is not easily made by the increase of internal pressure, that is, preventing the bag from bursting, whereby the contents do not flow out into the hot water by not easily communicating between the inside of the bag sheet and the outside of the bag sheet.

In particular, by forming the skin layer, the required pressure resistance strength is readily applied to the pressure release seal part, whereby the pressure resistance strength suitable for the purpose to which achieve compatible of deaeration at the time of microwave heating and a sealability at the time of heating in hot water can be easily realized. By forming the skin layer, the pressure release seal part is easily designed thereby leading to stability of quality.

Further, the present invention provides the structure in which by forming the bead part in the pressure release seal part together with the flat part, the pressure release seal part is less easily peeled off in the bead part than in the flat part, the entire pressure release seal part is prevented from being peeled off at once at the time of increasing the internal pressure, and the pressure resistance strength suitable for microwave heating and heating in hot water is readily ensured.

More specifically, after the research, the inventor of the present application found that the pressure resistance strength 6 to 30 kPa at 100° C. is suitable for satisfying both microwave heating and heating in hot water, thus, the present invention is able to provide the means for obtaining stably and easily the pressure resistance strength.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

(A) is a schematic sectional view showing a heating pouch according to the present invention, (B) is a partly cutaway enlarged sectional view of a bag sheet to form the heating pouch of (A), (C) is a sectional view taken along line X-X of (A), (D) is a partly cutaway enlarged sectional view showing important part of (C), (E) is a partly cutaway enlarged sectional view showing important part of (D), (F) is a partly cutaway enlarged sectional view showing important part of a state where a pressure release seal part of (D) is peeled off due to generation of steam in the pouch at the time of microwave heating, and (G) is an illustrative view showing transition of a peeling off strength of the heating pouch shown in (A) to 1(D).

FIG. 2

(A) is an illustrative view showing a process of manufacturing the heating pouch of FIG. 1(A), (B) is an illustrative view showing a subsequent process to (A), (C) is an illustrative view showing a subsequent process to (B), (D) is an illustrative view with respect to a mechanism of intermittent feeding of a plastic film during the process of (A) to 2(C), and (E) is an illustrative view showing sizes of respective parts in an embodiment of the present invention.

FIG. 3

(A) is an illustrative view showing different manufacturing method of the heating pouch of the present invention, (B) is a partly cutaway enlarged sectional view showing important part of other embodiment with respect to a pressure release seal part of the heating pouch in the present invention, (C) is a partly cutaway enlarged sectional view showing important part of still other embodiment with respect to the pressure release seal part, (D) is a partly cutaway enlarged sectional view showing important part of further other embodiment with respect to the pressure release seal part, (E) is a partly cutaway enlarged sectional view showing important part of other embodiment of an easily peelable tape, (F) is a partly cutaway enlarged sectional view showing important part of other embodiment of the easily peelable tape, (G) is a partly cutaway enlarged sectional view showing important part of still other embodiment of the easily peelable tape, (H) is a partly cutaway enlarged sectional view showing important part of further other embodiment of the easily peelable tape, and (I) is a partly cutaway enlarged sectional view showing important part of furthermore other embodiment of the easily peelable tape.

FIG. 4

(A) is a partly cutaway enlarged sectional view showing important part of other embodiment with respect to the pressure release seal part, FIG. 4(B) is a partly cutaway enlarged sectional view showing important part of a forming method of the pressure release seal part shown in (A), (C) is a partly cutaway enlarged sectional view showing important part of a peeling off state of the pressure release seal part, (D) is a partly cutaway enlarged sectional view showing important part of still other embodiment with respect to the pressure release seal part, (E) is a partly cutaway enlarged sectional view showing important part of further other embodiment with respect to the pressure release seal part, and (F) is an illustrative view showing transition of a peeling off strength of the pressure release seal part shown in (D).

FIG. 5

(A) is a partly cutaway enlarged sectional view showing important part of other example of the forming method of the pressure release seal part, and (B), (C), (D), and (E) are a partly cutaway enlarged sectional view showing important part of forming methods other than (A).

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be explained based on the drawings.

As for the shape of a heating pouch serving as a heating package in the present invention, any shapes such as such three-sided seal, four sided-seal, flat-typed butt-seam bag, and butt-seam gazette bag or the like can be arbitrary selected. In addition, the heating pouch can be implemented to automatically filling the contents while making the pouch, but also after making the pouch as the bag sheet in advance, contents are filled and the bag sheet is sealed.

(Basic Configuration)

FIG. 1(A) shows a heating pouch 1 in a state where contents are housed. The heating pouch 1 in this embodiment is a bag sheet 10 providing an easily peelable seal part as a pressure release seal part 2. The pressure release seal part 2 is to form a seal such that a part of a sheet constituting the bag sheet 10 is overlapped with a different part of the sheet, the pressure release seal part 2 is peeled off at the time of an internal pressure rises due to microwave heating so as to form a deaeration passage which communicates between the inside of the heating pouch 1 and the outside of the heating pouch 1. The pressure release seal part 2 is to release steam, and the final purpose of the pressure release seal part 2 is to release the pressure in the heating pouch 1 which is the bag sheet 10.

In this example, as shown in FIGS. 1(A) and (C), the bag sheet 10 provides a lower sheet part 12 and an upper sheet part 11 arranged on the lower sheet part 12 so as to overlap each other and is a substantially rectangular shape in a plan view to house a food product f between the lower sheet part 12 and the upper sheet part 11.

The pressure release seal part 2 having an easily peelable property is provided in the upper sheet part 11. That is, the pressure release seal part 2 is formed by adhering a part of the upper sheet part 11 with other part of the upper sheet part 11 so as to overlap in butt-seam shape. The pressure release seal part 2 will be explained more specifically later.

In the heating pouch 1 having a substantially rectangular shape in a plan view, the lower sheet part 12 and the upper sheet part 11 are sealed respectively at a front end side 3 a, a back end side 3 b, right end side 3 c, and left end side 3 d respectively to seal the food product f. The sealing can be performed by heat seal.

In order to distinguish the above each end sides of the heating pouch 1 from the pressure release seal part 2 which forms the deaeration passage, the each end sides will be called connecting parts as necessary. Specifically, each end sides will be called as follows; the front end side 3 a after sealing is the front connecting part 3 a, the back end side 3 b after sealing is the back connecting part 3 b, the right end side 3 c after sealing is the right connecting part 3 c, and the left end side 3 d after sealing is the left connecting part 3 d.

In FIG. 2(C), as shown right and left bag sheets 10 shown in the uppermost part, any one of the right end side 3 c and left end side 3 d of the heating pouch 1 before housing the food product is open, and after the food product is housed, the open end side is sealed as shown in FIGS. 1(A) and (C).

In this example, the upper sheet part 11 and the lower sheet part 12 constituting the bag sheet 10 are formed by one plastic film p. Accordingly, the upper sheet part 11 and the lower sheet part 12 are connected even before housing the food product at any one of the right end side 3 c and left end side 3 d. That is, when the bag sheets in the uppermost part of FIG. 2(C) are taken as an example, the right bag sheet 10 opens the left end side 3 d and closes the right end side 3 c from the beginning, and the left bag sheet 10 opens the right end side 3 c and closes the left end side from the beginning.

The bag sheet 10 may be plastic having heat resistance to a microwave heating. As shown in FIG. 1(B), the bag sheet 10 has a base material 10 a and a sealant layer 10 b. The sealant layer 10 b is a layer laminated on one side of surface of the base material 10 a.

As for the base material 10 a, a plastic material having a heat resistance to microwave heating is used. For example, the base material 10 a can be formed by a material such as a biaxially stretched film consisting of polypropylene, polyamide, polyester, ethylene-vinylalcohol copolymer and so on, a vinylidene chloride-acrylic acid ester copolymer film, an aluminum oxide deposition biaxially stretched polyester film, and a polymetaxylylene adipamide polyamide stretched film (including a coextruded laminated film with 6-nylon). However, as long as the material has heat resistance to microwave heating, the heating pouch can be implemented by adopting a plastic material other than the above materials as the base material 10 a.

As for the sealant layer 10 b, a film excellent in both a seal strength and a mechanical strength, having a heat resistance and a strength to withstand thermal sterilization and microwave cooking, and excellent in a contents resistance such as an oil resistance is used. Specifically, as such a film, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, homo polypropylene, random copolymerization polypropylene, block copolymerization polypropylene, α-olefin copolymer, and others, and a blend thereof can be mentioned. The sealant layer 10 b is not peeled off due to softening even at the time of microwave heating and heating in hot water.

Although not shown in the figures, an opening notch is formed on at least any one of the connecting parts 3 a to 3 d. The notch may be a starting point at the time of breaking off the bag sheet 1 and as a slit that makes opening easy. The notch may be a V shaped cutout part, alternatively for example, the notch may be a U shaped cutout part, or a simple slit on a single line.

(Pressure Release Seal Part 2)

The pressure release seal part 2 described above preferably has a pressure resistance strength 6 to 30 kPa at 100° C.

As a numerical value for preventing break-off while heating in hot water including boiling sterilization other than heating for cooking. The pressure release seal part 2 has a lower limit value of the pressure resistance strength 6 kPa at 100° C. in such above. When boiling sterilization is taken as an example, this lower limit value of the pressure resistance strength is a numerical value for preventing break-off under the condition that is immersed in water tank at 95° C. from water surfaces to several tens of centimeters below. That is, upon boiling sterilization, depending on the method, there is a necessity to withstand the water pressure several tens of centimeters below the water surface in the water tank at 95° C. so as to avoid break-off, thus the numerical value is limited to the above lower limit value. In particular, in order to more reliably prevent the break-off, the lower limit value is preferably set to 8 kPa.

As described above, the pressure release seal part 2 has an upper limit value of the pressure resistance strength of 30 kPa at 100° C. This upper limit value is a particularly preferable numerical value to ensure a steam releasing property at the time of microwave heating. This is because steam releasing is required due to the internal pressure by water vapor generated from the food product by microwave heating. In this example, particularly in order to perform releasing steam more reliably, the upper limit value is preferably set to 25 kPa.

By setting the upper limit value of the pressure resistance strength to 30 kPa, when the internal pressure of the heating pouch become over 30 kPa, steam generated in the pouch is smoothly released without making noise.

Through the position of the seal strength, the pressure release seal part 2 can be implemented by setting the seal strength 1.3 to 20 N/15 mm at 100° C.

Further, through the position of a ratio of initial peak value/intermediate value, the pressure release seal part 2 can be implemented by setting “initial peak value/intermediate value” of the seal strength 1.3 to 3.0 at 100° C.

Although the above numerical value ranges are the most desirable, as long as both microwave heating and heating in hot water can be compatible, the strengths and the ratio may be slightly deviated from the ranges of the above strengths and the ratio.

This pressure release seal part 2 in the embodiment will be further specifically explained.

As shown in FIGS. 1(A) and (D), the pressure release seal part 2 provides a first seal mechanism 21 and steam ports 8.

(First Seal Mechanism 21)

The first seal mechanism 21 is provided with an easily peelable tape 20. The easily peelable tape 20 is provided with a tape main body 4 serving as easily peelable layer and a skin layer 5. Hereinafter, the tape main body 4 will be called the easily peelable layer 4 as necessary.

As shown in FIG. 1(D), the easily peelable tape 20 is inserted between a part of the upper sheet part 11 and other part of the upper sheet part 11 which is overlapped with the sheet in butt-seam. The skin layer 5 is provided on the front surface side of the easily peelable tape 20 serving as an top surface of the easily peelable tape 20, whereby a seal surface m is formed on the front surface side of the easily peelable tape 20. In this example, a lower surface of the easily peelable tape 20, that is, a back surface of the tape main body 4 is directly adhered on the upper sheet part 11. In the example shown in FIG. 1(D), the skin layer 5 is only formed on one side of the surface of the easily peelable tape 20.

In such above, in the case that the easily peelable tape 20 in which the skin layer 5 is formed on the tape main body 4 is used, as entire pressure release seal part 2, as described above, the pressure resistance strength is set to 6 to 30 kPa at 100° C., and more preferably, the pressure resistance strength is set to 8 to 25 kPa at 100° C.

For the skin layer 5, resin having tensile yield stress (JIS K 7161, 7162) of 10 to 40 MPa, being able to perform heat sealing, attracting the seal strength of 30 N/15 mm or more under a normal state is used.

Specifically, the skin layer 5 may be formed by polyolefin resin. Alternatively, as the skin layer 5, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, homo polypropylene, random copolymerization polypropylene, block copolymerization polypropylene, α-olefin copolymer, or others, or a blend thereof can be used.

A manufacturing method of the skin layer 5 includes the methods comprising, forming a film by co-extrusion with other layer, directly applying by extrusion lamination method, and applying a film by dry lamination method. However, this does not exclude the formation of the skin layer 5 by the other well-known methods.

The tape main body 4 is formed by a high temperature dependent film and comprises the easily peelable layer.

For the tape main body 4, a material such as polyolefin resin including polypropylene resin and polyethylene resin, or polyester resin, etc., which has a heat sealing property with respect to the sealant layer 10 b can be used.

Here, explaining a peeling off mechanism of the easily peelable layer, as the peeling off mechanism, there are (a) interfacial peeling off, (b) interlayer peeling off, and (c) agglomeration peeling off, which can be selectively or combinedly used depending on the cases.

(a) Interfacial peeling off means that easily peeling off is carried out at interface of a bag main body (sheet constituting the bag sheet) and the insertion tape (easily peelable tape 20). Therefore, this does not relate a case that the easily peelable layer 4 exists in an intermediate layer (there is no interfacial peeling off).

(b) Interlayer peeling off means that peeling off is carried out in the interlayer between the skin layer 5 and the easily peelable layer 4 after the skin layer 5 is teared off, the tensile yield stress of the skin layer 5 and interlayer adhesion strength between the skin layer 5 and the easily peelable layer 4 affect a peeling off strength.

(c) Agglomeration peeling off means that the material itself of the easily peelable layer 4 is destroyed, and agglomeration force is adjusted by properly preparing a dispersion phase in a continuous phase to manufacture.

In the case that the easily peelable layer 4 exist in the intermediate layer, a strength at the time of tearing off the skin layer 5 is also affected.

As for Resin blending to form the easily peelable layer 4 as the agglomeration peelable layer, illustrative example thereof can be described blending polybutene with low-density polyethylene.

A thickness of the skin layer 5 is 3 to 40 μm, preferably 3 to 30 μm, more preferably 3 to 15 μm. The thickness of the skin layer 5 is the most preferably 5 to 15 μm.

As described later in the description of the manufacturing method, by inserting the easily peelable tape 20 into between creases of the plastic film p before being formed into a butt-seam shape, the skin layer 5 can be provided in the pressure release seal part 2.

In this example, as the skin layer 5, the high temperature dependent film such as a linear low-density polyethylene based material is laminated on the tape main body 4 to be formed.

In this example, the skin layer 5 is a polyolefin layer, the skin layer 5 is a layer formed on the easily peelable tape 20, that is, the front surface of the tape main body 4 by coextruding the film forming the tape main body 4 and polyolefin.

In this example, the formation of the skin layer 5 provides the seal surface m on the front surface of the easily peelable tape 20 (tape main body 4) to be coated. At the time of microwave heating, the strength of the high temperature dependent easily peelable layer is lowered due to a pressure rises by heating, and as shown in FIG. 1(F), the skin layer 5 is teared off by inflation of the pouch whereby the pressure release seal part 2 is peeled off to be able to release the steam. The reference number 5 a in FIG. 1(F) shows a tear of the skin layer 5.

When easily peelable tape 20 is heated to a temperature higher than room temperature, the easily peelable tape 20 becomes to easily peel off from the bag sheet 10 due to a steam pressure in the bag than at the time of the room temperature, and by adjustment of the skin layer 5, a design can be made so as to readily provide a required peeling off strength, and further, the peeling off strength can be stabilized.

That is, the easily peelable tape 20 in which the skin layer 5 is formed is different from an easy peel which is easily opened by human hands at the room temperature but provides a tape having a property of being reliably peeled off when the pressure reaches a predetermined pressure by heating. Therefore, by the easily peelable tape 20, a design can be easily made so as to reliably open the bag sheet 1 at the time of the internal pressure rises upon microwave heating. The materials for the skin layer 5 can be implemented by employing the well-known material other than the materials shown in the examples. As described above, the easily peelable tape 20 can be implemented as a further multiple layer provided with a layer other than the skin layer 5 together with the skin layer 5 as long as the skin layer 5 is arranged on the front surface of the easily peelable tape 20.

A relationship between the bag sheet 10 and the easily peelable tape 20 shown in FIG. 1(D) will take into account in more detail. As shown in FIG. 1(E), the skin layer 5 is provided with the seal surface m to adhere to the sealant layer 10 b of the bag sheet 10 so as to be peeled off at the time of the pressure increase.

For example, as shown in FIG. 1(E), in the bag sheet 10, the sealant layer 10 b has 60 μm thick, and the base material 10 a is biaxially stretched polyamide film having 15 μm thick. In the example shown in FIG. 1(E), in the pressure release seal part 2, the tape main body 4 is 25 μm thick, and the skin layer 5 is 5 μm thick. However, regarding the thicknesses of the layers, the numerical values mentioned above are illustrative examples. As long as the peeling off strength for compatible of both microwave heating and heating in hot water can be ensured, the numerical values can be changed into other numerical values for implementation.

Meanwhile, the peeling off strength between the layer of the tape main body 4 and the layer of the upper sheet part 11 is stronger than the peeling off strength in the skin layer 5.

The pressure release seal part 2 is formed on over the substantially entire region in the front to back width direction between the front end side 3 a and the back end side 3 b. The entire region in the front to back width direction may be evenly peeled off, however, specifically it is preferable to form steam ports 8 so that the predetermined position in the front to back width direction of the pressure release seal part 2 is peeled off in preference to the other position in front to back width direction than the that of position.

That is, it is preferable that the steam ports 8 be provided as pressure release parts at the time of the pressure increase by microwave heating for the heating pouch so that water vapor be reliably discharged to outside from the steam ports 8.

As shown in FIG. 1(A), the steam ports 8 are provided on a part of the upper sheet part 11 covering the easily peelable tape 20 and arranged in an intermediate part between the front end side 3 a and the back end side 3 b of the pressure release seal part 2. The steam port 8 is a cutout part to cut out from the front end 2 a side of the pressure release seal part 2 toward the base part side of the pressure release seal part 2 (to a depth not reaching to the base part). Further, the steam port 8 is also a non-adhering part that does not seal the bag sheet 10. By inflation of the heating pouch 1 at the time of microwave heating, the pressure release seal part 2 stands up (in the direction shown by an arrow Y), and the steam port 8 becomes the uppermost part of the heating pouch 1 (FIG. 1(C)).

At the time of inflation by microwave heating, the steam is not released from the steam ports 8 all at once, but toward the direction shown by the arrow Y of FIG. 1(C), in the pressure release seal part 2, that is, the easily peelable tape 20, steam is released gradually from the steam ports 8 by an effect of the skin layer or a bead layer.

The present invention also can be implemented that the easily peelable tape 20 is provided with a base layer 9 shown in FIG. 3(E), in addition to the easily peelable layer 4 and the skin layer 5.

Similarly to the skin layer 5, for the base layer 9, resin having tensile yield stress (JIS K 7161, 7162) of 10 to 40 MPa, being able to perform heat sealing, attracting the seal strength of 30 N/15 mm or more under a normal state is preferably used.

That is, the skin layer 9 may be formed by polyolefin resin.

Alternatively, as the skin layer 9, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, homo polypropylene, random copolymerization polypropylene, block copolymerization polypropylene, α-olefin copolymer, or others, or a blend thereof can be used.

The base layer 9 may be two or more layers, and any one of the layers not placed on the seal surface may be a biaxially stretched polyester film, a biaxially stretched polyamide film, a biaxially stretched polypropylene film, a non-stretched polypropylene film, and other films, thus, an effect of preventing stretching can be provided.

(Manufacturing Method of First Seal Mechanism 21)

The manufacturing method of the heating pouch shown in FIGS. 1(A) to 1(D) will be summarized and described.

This manufacturing method is to execute the following processes 1) to 5).

1) Step of Folding

In a manufacturing line, while continuously supplying one strip-shaped plastic film p provided with the base material 10 a and the sealant layer 10 b, the sealant layer 10 b side of the plastic film places inward and the plastic film is folded into the Japanese hiragana syllabary Hi (the shape shown in FIG. 2(A)) by using a guide plate. Specifically, as shown in FIG. 2(A), in the end surface view of the strip-shaped plastic film p, the plastic film is made to a flat bottom shaped bag with an open upper part, and in the upper part of the bag, left side end v and right side end w of the plastic film p are folded into a gazette shape so as to extend laterally to the outside of the bag. In FIG. 2, the reference signs 16 denote left and right folded parts on the bottom of the above gazette.

2) Step of Inserting Tape

In parallel to the above folding step, in a step for inserting tape, while inserting the easily peelable tapes 20, the plastic film p is carried out final folding by the guide plate (not illustrated) and closed into a gazette shape.

That is, as shown in FIG. 2(B), the left side end v and right side end w are folded inward to be faced with each other as shown in the lowermost part of FIG. 2(C). The reference number 13 in FIG. 2(B) shows folding line to fold the side end v and the side end w inward.

The reference number z in FIG. 2(C) shows the feeding direction of the plastic film p.

In the state shown in FIG. 2(C), the right end side 3 c serving as the right connecting part 3 c and the left end side 3 d serving as the left connecting part 3 d are not respectively bonded by sealing but the folding line which is formed by folding a single sheet as a gazette bag.

3) Step of Intermittent Feeding

Through the above dancer rolls d shown in FIG. 2(D), a flow of the plastic film p is made to move intermittently. Specifically, a line to feed the plastic film p is provided with plural rollers that move the plastic film p and further guide the movement. Each of the rollers is drawn as circles in FIG. 2(D). The dancer rolls d among the rollers can be moved upward and downward which is different from the other rollers whose positions are fixed. In the above line, the plastic film p is continuously fed on the upstream side z1 of the dancer rolls d. Meanwhile, in the downstream side z2 of the dancer rolls d, the plastic film p is intermittently fed by upward and downward movement of the dancer rolls d.

4) Step of Forming Steam Port

The steam ports 8 are formed in a vertical sealing device (not shown), and steam port seal end parts, that is, ear parts 13 a near the folding line 13 are removed by slits.

5) Step of Side Seal

In a side sealing device (not shown), by heat sealing the left and right folded parts 16, side seal parts, that is, the right connecting part 3 c and left connecting part 3 d are formed. However, the right end side 3 c serving as the right connecting part 3 c and the left end side 3 d serving as the left connecting part 3 d may not be respectively bonded by sealing but may remain the folding line.

6) Step of Lateral Seal

In the downstream side of the dancer rolls d, in a lateral sealing device (not shown), lateral seals 3 e are formed by intermittently sealing in the direction intersecting with the feeding direction of the plastic film p.

7) Step of Cutting Lateral Seal

In the lateral seals 3 e, the plastic film p is divided along the lateral direction by cutting machine (not shown). By this division, a pair of left and right bag sheets 10 is sequentially formed.

(Advantage of the Above Manufacturing Method)

Through the above steps 1) to 7), the pouch for microwave heating which has pair of left side and right side as well as two laterally-placed can be effectively manufactured. At the end, the lower sheet part 12 is cut, as shown in the uppermost part of FIG. 2(C), and the two symmetrical bag sheets can be formed.

By the method shown in FIG. 2, according to general bag, the pouch for microwave heating can be effectively manufactured with two laterally-placed.

Use of the easily peelable tape is advantageous in terms of quality stabilization and cost in comparison to a case that parting agent application, corona treatment, etc., is performed as an easy opening treatment to provide an easily openable property to a particular point of the bag sheet 10.

Further, by the dancer rolls d being attached to the facility, the plastic film p can be folded while continuously flowing. Thereby, variation in folding size related to the flowing direction is suppressed. There is an effect of preventing that a folding position is displaced downstream from the dancer rolls or the folds are opened, leading to prevention of failure generation, quality stabilization, and reduction in a loss ratio.

Furthermore, by making the dancer rolls d large diameter rolls having a diameter larger than the other rollers constituting the line or projecting/recessing a roll circumference, a change in the folding position can be suppressed.

By inserting the easily peelable tape at the timing shown in the step 2) which is step of inserting tape, the tape can be inserted to a fixed position without any stress. If the insertion is implemented downstream than this position, the tape has to move in the lateral direction by a (substantially) length of the bag. This leads to failure such as the tape folding, reversing, and damage to the tape.

(Transition of Peeling Off Strength of First Seal Mechanism 21)

By taking the pouch having the first seal mechanism 21 shown in FIG. 1(D) to (F) as an example, transition of the peeling off strength of the pressure release seal part 2 at the time of the pressure increase by heating is shown in FIG. 1(G). The vertical axis of FIG. 1(G) indicates the peeling off strength, and the horizontal axis indicates time.

A peak of the peeling off strength serving as an initial value appears in a part of the graph of FIG. 1(G) enclosed by a single chain circle. As subsequently shown by an intermediate value enclosed by a broken line circle, the peeling off strength is lowered and stably transitioned. From this, it can be understood that a large peeling off strength at the initial stage of pressurization where the skin part 5 shown in FIG. 1(F) is teared off is ensured, and after the skin layer 5 is teared off, the peeling off strength is lowered, and the peeling off strength which is stabilized in a certain state can be ensured.

(Modified Example of Configuration of Bag Sheet 10)

In the embodiment shown in FIG. 2, the upper sheet part 11 and the lower sheet part 12 constituting the bag sheet 10 are respectively formed by a single plastic film p. In addition, as shown in FIG. 3(A), the upper sheet part 11 and the lower sheet part 12 are to be respectively formed as plastic films p, the bag sheet can be implemented as one integrated by sealing each of the right side ends 3 c as well as each of left side ends 3 d. FIG. 3(A) shows a state viewed from the same direction with FIG. 2(C) shown the lowermost part.

(Modified Example of Pressure Release Seal Part 2 Having First Seal Mechanism 21)

Unlike the embodiment shown in FIG. 1(D), the easily peelable tape 20 can be implemented by being provided a run-over part h as shown in FIG. 3(B). The run-over part h is a part projecting to the inside of the bag of the heating pouch 1, that is, to the housing space k side of the food product in the easily peelable tape 20.

In any case that whether the run-over part h is provided or not, the skin layer 5 may be provided on the upper surface side of the tape main body 4 or may be provided on the lower surface side of the tape main body 4.

In the easily peelable tape 20 of the embodiment shown in FIGS. 1(D) to 1(F), the skin layer 5 is provided only on one surface, that is, the front surface (upper surface) of the easily peelable tape 20 (tape main body 4). In addition, as shown in FIG. 3(C), the easily peelable tape 20 can be implemented by providing the skin layers 5 on the both surfaces, that is, on both of the front surface side and the back surface side of the tape main body 4. FIG. 3(C) shows a state where the seal surface of the skin layer 5 on the upper surface side of the tape main body 4 is peeled off at the time of microwave heating. However, at the time of microwave heating, the seal surface of the skin layer 5 on the lower surface side of the tape main body 4 may be peeled off or both the upper and lower skin layers 5 may be peeled off.

In the example shown in FIG. 3(A), when both the upper and lower skin sides of layers 5 are the same configuration, in order to peel off the upper skin layer 5 above the tape main body 4 as shown in FIG. 3(C) at the time of microwave heating, unlike the sealant layer 10 b to be adhered to the skin layer 5, it is necessary to set the sealant layer 10 b which is adhered to the non-peeled off skin layer 5 to have peel off strength not peeling off due to the generation of water vapor.

If necessary, the skin layer 5 peeling off from the sealant layer 10 b at the time of steam generation will be called peeled off skin layer 5 h, the sealant layer 10 b adhered to the peeled skin layer 5 h will be called the peel off side sealant layer 10 h, the skin layer 5 not peeled off from the sealant layer 10 b at the time of steam generation will be called the non-peeled off skin layer 5 n, and the sealant layer 10 b adhered to the non-peeled off skin layer 5 n will be called the non-peeling off side sealant layer 10 n. In this case, the bag sheet 10 is constituted by respective different sheet members of a sheet member comprising a sheet member having base material 10 a and the peeling off side sealant layer 10 h (hereinafter, referred to as first sheet member 14), and a sheet member comprising the base material 10 a and the non-peeling off side sealant layer 10 n (hereinafter, referred to as second sheet member 15).

The peeling off side sealant layer 10 h of the first sheet member 14 is of the condition and the composition already described in FIG. 1(D), whereas under the pressurizing condition of peeling off the peeling off skin layer 5 h from the peeling off side sealant layer 10 h, the non-peeled off skin layer 5 n in the second sheet member 15 is set to a sealed stat adjusted to a peeling off strength that does not peel off from the non-peeling off side sealant layer 10 n(the run-over part is reduced more than the opposite pressure release seal part 2 or eliminated), or adjusted material is employed. That is, the peeling off strength may be achieved by both selection of the material constituting the pressure release seal part 2 and adjustment of the sealing situation.

The pressure release seal part 2 is formed between connecting parts of the two bag sheets, the manner in which these two bag sheets are connected can be implemented with various changes, however, it is preferable to implement by adopting a butt-seam seal.

Most preferably, it is advantageous to implement adjustment in the form as shown in FIG. 5(A) because the sealing situation can be easily adjusted.

Specifically, as an adjustment method of the sealing situation, a shape of the butt-seam seal is adopted, a length of the run-over part h, the non-peeling side (between the upper sheet part 11 on the upper side u1 and the easily peelable tape 20) is set to be shorter than the peeling side (between the upper sheet part 11 on the lower side u2 and the easily peelable tape 20). When rephrasing with a length of a zone to be sealed, a length of a zone where a non-peeling off side seal g1 is formed (between the upper sheet part 11 on the upper side u1 and the easily peelable tape 20) is set to be longer than a length of a zone where an easy peeling side seal g2 is formed (between the upper sheet part 11 on the lower side u2 and the easily peelable tape 20) (in the each figures of FIG. 5, the above non-peeling off side seal g1 and the easy peeling off side seal g2 are regions respectively shown by bold dots).

At the time, when the easy peeling off side seal g2 is placed on the lower side (the skin layer 5 is placed on the lower side of the easily peelable layer 4), the above structure can be highly easily realized. In particular, it is advantageous that the longer side and the shorter side of the run-over part h can be formed by a single sealing action at minimum. This is because an inner end of the easy peeling off side seal g2 is fixed at a folded position shown in the reference sign T in FIG. 5(A) of the double-folded upper sheet part 11 on the lower side u2, whereas a sealing position of an inner end of the non-easy peeling off side seal g1 can be arbitrarily adjusted only by modifying a position of a seal plate S. Since the upper sheet part 11 on the upper side u1 is closer to the seal plate S than the upper sheet part 11 on the lower side u2, a seal g0 due to remaining heat can be obtained (region shown by light dots in FIG. 5(A)).

The reference sign S0 in the figures denotes a receiving base corresponding to the seal plate S.

As a comparative example for this, FIG. 5(C) can be shown. This shows a case that the skin layer 5 and the easy peeling layer 4 are placed upside down and the lengths of the run-over part h are also made opposite to each other. In this case, the longer side and the shorter side of the run-over part h have to be formed individually by seals. Moreover, in order to form the non-easy peeling off side seal g1, the upper sheet part 11 on the upper side u1 has to be separated once so as not to be sealed (see FIG. 5(B)). Next, after the upper sheet part 11 on the upper side u1 is placed over the original position, the easy peeling off side seal g2 (the longer side of the run-over part h) is formed (FIG. 5(C)). This method has a problem that the facility is complex and broad, tasks are much more complicated, production efficiency is dropped, and a failure generation ratio is increased.

As another comparative example, a peeling agent g3 can be partially applied for extending the run-over part h of the non-easy peeling off side seal g1 (FIG. 5(D)), or a sheet g4 having a parting property can be sandwiched so as not to be sealed (FIG. 5(E)). However, this example also has a problem that the number of treatment processes is increased and the production efficiency is dropped.

As described above, although FIG. 5(A) is the most advantageous, upon implementation of the present invention, it is not impossible to implement as shown in the other figures of FIG. 5.

Even in a case that the skin layers 5 are provided on both the front and back surfaces of the easily peelable tape 20, the easily peelable tape can be implemented by including the same run-over part h in FIG. 3(B) as shown in FIG. 3(D).

In cases of FIGS. 3(C) and (D), a thickness of both the skin layers 5 is 5 μm, and thicknesses of the other layers constituting the bag sheet 10 and the pressure release seal part 2, the layers being other than the skin layers 5 are the same as the layers of FIG. 1(E) described above.

Meanwhile, the above numerical values of the thicknesses of the above layers are illustrative examples, thus, as long as the above peeling off strength for achieving both microwave heating and heating in hot water can be ensured, the numerical values can be changed into other numerical values for implementation.

In the embodiments shown in FIG. 3(A) to (D), matters not specifically mentioned are the same as the embodiment shown in FIGS. 1 and 2.

Further, other embodiments of the easily peelable tape 20 are shown in FIG. 3(F) to (I).

An easily peelable tape 20 shown in FIG. 3(F) is constituted by the easily peelable layer 4 and the base layer 9.

In an easily peelable tape 20 shown in FIG. 3(G), the easily peelable layers 4 are provided on the front surface side and the back surface side (both upper and lower surfaces) of the base layer 9, and the skin layers 5 are further laminated on both the easily peelable layers 4, so that the skin layers 5 are on the front and the back of the easily peelable tape 20.

An easily peelable tape 20 shown in FIG. 3(H) is constituted only by the easily peelable layer 4, not comprising the skin layer 5 and the base layer 9.

An easily peelable tape 20 shown in FIG. 3(I) is constituted by the base layer 9 and the easily peelable layers 4 laminated on the front surface side and the back surface side (both upper and lower surfaces) of the base layer 9, not comprising the skin layer 5.

In the embodiments shown in FIG. 3(E) to (I), matters not specifically mentioned are the same as the embodiments shown in FIGS. 1, 2, or FIG. 3(A) to (D).

A further another embodiment related to the pressure release seal part 2 is shown in FIG. 4(A). This pressure release seal part 2 comprises a second seal mechanism 22 and the steam ports 8. Since the steam ports 8 are the same as the pressure release seal part 2 including the first seal mechanism 21 shown in FIG. 1, description thereof is omitted.

(Second Seal Mechanism 22)

The second seal mechanism 22 comprises a flat part 6 serving as a flat seal surface m, and a projection-shaped resin bead part 7 projecting toward the inner surface side of the bag sheet 1 from the flat part 6. In this example, the inner surface side of the bag sheet 1 is the thickness direction of a sheet member opposed to the seal surface m, the sheet member being adhered to the seal surface m.

Even in the pressure release seal part 2 comprising the second seal mechanism 22, as the entire pressure release seal part 2 including configurations such as the flat part 6 and the bead part 7, a pressure resistance strength is set to 6 to 30 kPa.

However, the bead part 7 has a pressure resistance strength larger than that of the flat part 6.

In more detail, when general agglomeration peeling type easy peel resin is taken as an example, since a strength decrease under a high temperature is severe in comparison to PE (polyethylene) and PP (polypropylene) of uniform composition, it is pretty difficult to design within the range of the above peeling off strength. As a countermeasure for this, the method of increasing the peeling off strength only at the initial stage of peeling off is adopted, and as the method, the above second seal mechanism 22 including the bead part 7 is preferably adopted. The bead part 7 is a resin bead, that is, a bulge provided in the sealant layer 10 b at the time of sealing by sealing at a high temperature or high pressure. There is a merit that peeling becomes easy with an intermediate value of FIG. 4(F) to be described later.

The second seal mechanism 22 includes the bead part 7 serving as the above bulge at a position closest to the housing space kin the deaeration passage formed at the time of steam releasing, the deaeration passage running from the housing space k described above toward the steam ports 8, that is, the position serving as an inflow part from the inside of the bag to the deaeration passage.

Therefore, as shown in FIG. 4(A), the bead part 7 serving as the bulge part is arranged on the housing space k side from the above flat part 6. In such a way, an intermediate region on the bag outside of the bead part 7, that is, on the steam port 8 side is the above flat part 6 where no bead part 7 is provided.

A peeling off strength of the bead part 7 at the beginning of peeling is 1.3 to 3.0 times more than a peeling off strength of the flat part 6.

Specifically explaining, as shown in FIG. 4(A), in this case as well, the bag sheet 10 is constituted by the first and second sheet members 14 and 15 whose sealant layers 10 b have different properties from each other. The sealant layer 10 b of the first sheet member 14 placed above the bead part 7 serving as the peeling off side sealant layer 10 b is directly adhered to the flat part 6 provided in the sealant layer 10 b serving as the non-peeling off side sealant layer 10 b of the second sheet member 15 placed below the bead part 7. The non-peeling off side sealant layer 10 b functions in the same manner as the tape main body 4 of the easily peelable tape 20 described above. When the pouch is inflated by microwave heating, as shown in FIG. 4(C), the bead part 7 is peeled off the above peeling off side sealant layer 10 b and then the non-peeling off side sealant layer 10 b is peeled off the peeling off side sealant layer 10 b, so that the seal strength of the non-peeling off side sealant layer 10 b is lowered and steam can be released. That is, by lowering the seal strength of the non-peeling off side sealant layer 10 b, the deaeration passage described above is formed. Conversely to the example shown in FIG. 4(C), the sealant layer 10 b placed below the bead part 7 can serve as the peeling off side sealant layer 10 b to be peeled off the bead part 7, and the sealant layer 10 b placed above the bead part 7 can serve as the non-peeling off side sealant layer 10 b to be not peeled off the bead part 7 for implementation.

(Manufacturing Method of Second Seal Mechanism 22)

A forming method of the bead part 7 of FIG. 4(A) will be described. As shown in FIG. 4(B), the bead part 7 can be formed by placing a part of the upper sheet part 11 over a different part and heating and melting the sealant layers 10 b of both the parts in direct contact from the upper base material 10 a side by a seal bar s.

However, the bead part 7 may be formed by heating from the lower side of FIG. 4(B), from the base material 10 a side of the lower second sheet portion 15 by the seal bar s and melting the lower sealant layer 10 b in the figure. The bead part 7 can be formed by heating and melting both the upper and lower sealant layers 10 b for implementation.

In a case that the bag sheet is heated from any of the upper side and the lower side, a receiving member (not shown) facing the bag sheet may be provided on the opposite side of the seal bar s across the bag sheet. The bag sheet is sandwiched by the above receiving member with the seal bar s to perform the above heating by the seal bar s.

In the manufacturing method, matters not specifically mentioned are the same as the manufacturing method of the first seal mechanism 21 shown in FIG. 2.

(Transition of Peeling Off Strength of Second Seal Mechanism 22)

By taking the embodiment of FIG. 4(A) having the second seal mechanism 22 as an example, the transition of the peeling off strength of the pressure release seal part 2 at the time of the pressure increase by heating is shown in FIG. 4(F). In FIG. 4(F), the vertical axis indicates the peeling off strength, and the horizontal axis indicates time.

A peak of the peeling off strength appears as an initial value in a part enclosed by circled chain line in the graph shown FIG. 4(F), then as indicated by intermediate value which is enclosed by circled dotted line, the peeling off strength is lowered and stably transitioned. From this, it can be understood that, in the second seal mechanism 22 having the bead part 7, a large peeling off strength at the initial stage of pressurization is ensured in the bead part 7, and the peeling off strength stabilized at a certain peeling off strength can be ensured in the flat part 6.

(Modified Example of Pressure Release Seal Part 2 Having Second Seal Mechanism 22)

Other embodiments of the pressure release seal part 2 having the second seal mechanism 22 will be described.

As shown in FIG. 4(D), the second seal mechanism 22 can be implemented as having the easily peelable tape 20 which is a separate body from the bag sheet 10 in the same manner as the embodiments shown in FIG. 1(D) and FIG. 3(B) to (E). That is, in this modified example, the first seal mechanism 21 and the second seal mechanism 22 are provided together. However, this easily peelable tape 20 is comprised of only the tape main body 4 shown in the embodiments of FIG. 1(D) and FIG. 3(B) to (D). That is, in the example shown in FIG. 4(D), the easily peelable tape 20 is not provided with the skin layer 5. The easily peelable tape 20, that is, the front surface of the above tape main body 4 forms the flat surface 6, and further, the bead part 7 is provided on the front surface of the tape main body 4 together with the flat part 6. As shown in FIG. 4(E), the flat parts 6 and the bead parts 7 may be provided in both the front surface and the back surface of the easily peelable tape 20.

Although not shown, in the embodiments shown in FIGS. 4(D) and (E), the easily peelable tape 20 may be provided with the run-over part h projecting to the housing space k side.

The present invention can be implemented not only arranging the bead part 7 closer to the housing space k of the heating pouch 1, but also be implemented by arranging on the opposite side of the housing space k with the bead part 7 interposed therebetween, that is, on the front end 2 a side of the pressure release seal part 2.

Although not shown, the pressure release seal part 2 may be implemented by having both the first seal mechanism 21 and the second seal mechanism 22. That is, regarding the easily peelable tape 20, the skin layers 5 may be provided on the front surface and the back surface of the tape main body 4, further the bead parts 7 can project from both the skin layers 5 providing the seal surfaces m toward the bag sheet 10, that is, the upper sheet part 11 and break into the thickness part of the upper sheet part 11.

In the embodiments having the second seal mechanism 22 described in above, matters not specifically mentioned are the same as the embodiments in which the first seal mechanism 21 shown in FIGS. 1, 2, and FIG. 3(A) to (D) is provided, and description thereof is omitted.

(Summary)

In the second seal mechanism 22 having the bead part 7, in order to obtain a stable strength, the condition adjustment in each case is needed. In the first seal mechanism 21 having the skin layer 5, the deaeration passage is formed by tearing off the skin layer 5 due to the internal pressure at the time of the internal pressure increase by microwave heating, and in the first seal mechanism 21 having the skin layer 5, the targeted pressure resistance strength can be easily realized without drastically biasing the seal strength, thus in terms of stability, the first seal mechanism 21 is more excellent than the second seal mechanism 22. The skin layer 5 is easily designed, further, leading to stability of quality.

As described above, the deaeration passage is formed by tearing off the skin layer 5 at the time of the internal pressure increase by microwave heating.

EXAMPLES

(Example in which First Seal Mechanism 21 is Used in Pressure Release Seal Part 2)

Table 1 shows Examples 1 to 4 and Comparative Examples 1 to 3 using the first seal mechanism 21.

As shown in FIG. 2(E), in this heating pouch 1, left-right width, that is, lateral width t1 is 180 mm, front-back width, that is, vertical width t2 is 150 mm, left lateral width t3 between the left end and the base end of the pressure release seal part 2 is 150 mm, right lateral width t4 between the base end of the pressure release seal part 2 and right end is 30 mm, front-back width t5 of the front connecting part 3 a is 10 mm, and front-back width t6 of the back connecting part 3 b is 10 mm. The right connecting part 3 c is folded to form bottom part. Projecting width t8 from the base end to a front end of the pressure release seal part 2 is 10 mm.

After putting the contents in from the position of the left connecting part 3 d, the left connecting part 3 d is formed. A lateral width t7 of the left connecting part 3 d is 10 mm.

1) Preparation of Insertion Tape (Easily Peelable Tape 20)

A coextruded film comprised of three layers including the base layer 9, the easily peelable layer 4, and the skin layer 5 shown in FIG. 3(E) was manufactured and used. The thickness of the easily peelable layer 4 was adjusted to 10 μm, and the thickness of the skin layer 5 was adjusted to 0, 5, 15, 30, 40, 50 μm. Regarding the total thickness, only the skin layer 50 μm was 110 μm, the other layers was 70 μm, and the base layer 9 was adjusted to have such a thickness.

Material for the base layer 9 and the skin layer 5 was used Prime Polymer SP3530 (L-LDPE, density of 931 kg/cubic meter, and tensile yield stress of 13 MPa). The easily peelable layer 4 was prepared by blending Novatec LD LF 443(LDPE) of Japan Polyethylene Corporation and TAFMER BL3110M (polybutene) of Mitsui Chemicals Inc., by 80/20(%) respectively.

2) Preparation of Test Bag (Heating Pouch 1)

15 μm of ONy (Unitika ON-RT) and 50 μm of L-LDPE (Toyobo L-6101) were laminated by the dry laminate method and used. A bag of 150×180 mm (see the other paper for the size) was prepared, and the steam port parts were sealed with each insertion tape therebetween. Sealing was implemented under the condition that a sealing temperature is 160° C., a sealing period of time is one second, sealing pressure is 0.2 MPa, and the number of sealing to be implemented is twice.

3) Test Method 3-1-1) Pressure Resistance Strength at 100° C.

According to JIS Z0238 bursting strength test of container, the test bag was filled with air then sealed, air was fed into the bag at the amount of 1.0 L/min in an air bath kept at 100° C., and the pressure at the time of steam releasing or break-off of the bag was measured to obtain the pressure resistance strength.

3-1-2) Seal Strength at 100° C.

According to JIS Z0238 heat seal strength test, the steam port part was cut to the width of 15 mm, in the air bath maintained at 100° C., the seal strength (the peak value and the intermediate value) was measured under the condition that the tensile speed is 300 mm/min and the peeling angle is 180 degrees.

3-2) Microwave Steam Releasing Test

150 g of water was filled and packaged to subject to the test. By heating in a 600 W microwave for three minutes, it was confirmed that whether steam releasing is properly carried out.

3-3) Boil Sterilization Adequacy

150 g of water was filled and packaged to subject to the test. By immersing a test body in a boil sterilization tank (the water temperature of 95° C. and the water depth of 60 cm) for one hour, it was confirmed that whether the bag was break-off.

3-4) Heating in Hot Water Adequacy

A test body was put into a deep hot pot (diameter of 24 cm and capacity of 4.5 L) and filled with hot water into the deep hot pot, then heating is carried out for thirty minutes while maintaining a boiling state, it was confirmed that whether the bag was break-off or not.

(Test Results)

As shown in Table 1, in Examples 1 to 4, the thickness of the skin layer 5 is 5 to 40 μm, the pressure resistance strength at 100° C. is 8.6 to 28.2 kPa, the peak value of the seal strength at 100° C. is 1.62 to 17.1 N/15 mm, the intermediate value of the seal strength at 100° C. is 0.77 to 6.1 N/15 mm, and the initial peak value/intermediate value is 1.99 to 2.8.

In Examples 1 to 4, there was no problem in any of the microwave automatic steam releasing property, the boil sterilization adequacy, and the heating in hot water adequacy. That is, in Examples 1 to 4, in Table 1, there was no break-off of the bag as shown by YES in any of the microwave automatic steam releasing property, the boiling sterilization adequacy, and the heating in hot water adequacy.

Although Example 4 can be used as the heating pouch of the present invention, the example is inferior to the other embodiments (therefore, the evaluation is given YES—in Table 1), and the other embodiments are more suitable for the heating pouch of the present invention than Example 4.

Contrary to Examples 1 to 4, Comparative Example 1 is not provided with the skin layer 5, and the pressure resistance strength at 100° C. is 4.8 kPa, the peak value of the seal strength at 100° C. is 0.82 N/15 mm, the intermediate value of the seal strength at 100° C. is 0.75 N/15 mm, and the initial peak value/intermediate value is 1.09. In Comparative Example 2, the thickness of the skin layer 5 is 2 μm, the pressure resistance strength at 100° C. is 5.3 kPa, the peak value of the seal strength at 100° C. is 1.12 N/15 mm, the intermediate value of the seal strength at 100° C. is 0.78 N/15 mm, and the initial peak value/intermediate value is 1.44.

As shown in Table 1, in Comparative Examples 1 and 2, although the microwave automatic steam releasing property was recognized (“YES” in Table 1), break-off of the bag was occurred in both the boiling sterilization adequacy and the heating in hot water adequacy (“NO” in Table 1) as a result. Break-off of the bag in Comparative Examples 1 and 2 was occurred in the easily peelable layer 4 of the pressure release seal part 2 due to a weak seal strength.

In Comparative Example 3, the thickness of the skin layer 5 is 50 μm, the pressure resistance strength at 100° C. is 40.6 kPa, and the peak value of the seal strength at 100° C. is 36.7 N/15 mm.

As shown in Table 1, in Comparative Example 3, although there was no problem in both the boil sterilization adequacy and the heating in hot water adequacy, break-off of the bag was occurred and the evaluation “NO” was given to the microwave automatic steam releasing property.

Break-off of the bag in Comparative Example 3 was occurred after the sheet member 14 was stretched by the internal pressure. This is due to the fact that in a situation where the easily peelable layer 4 cannot be easily peeled off, in general, a weakest strength part including the seal parts 3 a to 3 d and the first and second sheet members 14, 15 was broken.

Details of the test results shown in Table 1 will be described later as evaluation results of Examples with evaluation of Example 5 shown in Table 2.

As described above, the test for the seal strength of Table 1 was performed according to 7. Bag Heat Seal strength Test of JIS Z 0238: 1998 (Test Method of Heat Sealing Soft Package Bag and Semi-Rigid Container). The test for whether occurring the break-off of the bag was performed according to 8. In addition, Container Bursting Strength Test of JIS Z 0238: 1998. Correction of a load in 7. Bag Heat Seal strength Test is accord to JIS P 8113 (Paper and Paperboard—Test Method of Tensile Property—Section 2: Constant Rate Extension Method).

Item Unit Comp. Ex. 1 Comp. Ex. 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Comp. Ex. 3 Thickness of skin μm 0 2 5 15 30 40 50 layer Pressure resistance kPa 4.8 5.3 8.6 8.8 9.0 28.2 40.6 strength at 100° C. Seal strength at 100° C. N/15 mm 0.82 1.12 1.62 1.69 1.64 17.1 36.7 (peak value) Seal strength at 100° C. N/15 mm 0.75 0.78 0.77 0.85 0.79 6.1 (intermediate value) Peak value/ 1.09 1.44 2.10 1.99 2.08 2.8 intermediate value Microwave automatic YES YES YES YES YES YES- NO steam releasing (break-off) property Boil sterilization NO NO YES YES YES YES YES adequacy (break-off) (break-off) Heating in hot water NO NO YES YES YES YES YES adequacy (break-off) (break-off) (Example in which Second Seal Mechanism 22 is Used to Pressure Release Seal Part 2)

Table 2 shows a test result of Example 5. Example 5 is the type shown in FIG. 4(A) in which the second seal mechanism 22 is employed and the bead part 7 is provided. Therefore, in Example 5, the skin layer 5 is not provided unlike Examples 1 to 4 in Table 1. In Example 5 shown in Table 2, the test method and the manufacturing method of the test bag are the same as those shown in Table 1, and the size and the configuration of the heating pouch 1 are also the same with FIG. 2(E) as described above.

As shown in Table 2, in Example 5, a size of the bead part 7, that is, a projecting width of projecting from the flat part 6 which is the seal surface m is 13 μm, the pressure resistance strength at 100° C. is 8.7 kPa, the peak value of the seal strength at 100° C. is 1.67 N/15 mm, the intermediate value of the seal strength at 100° C. is 0.82 N/15 mm, and the initial peak value/intermediate value is 2.04.

Regarding the test result of Example 5, as shown in Table 2, no break-off of the bag was occurred in any test of the microwave automatic steam releasing property, the boil sterilization adequacy, and the heating in hot water adequacy.

TABLE 2 Item Unit Comp. Ex. 1 Thickness of skin layer μm 0 Size of bead μm 13 Pressure resistance strength at 100° C. kPa 8.7 Seal strength at 100° C. (peak value) N/15 mm 1.67 Seal strength at 100° C. (intermediate N/15 mm 0.82 value) Peak value/intermediate value 2.04 Microwave automatic steam releasing YES property Boil sterilization adequacy YES Heating in hot water adequacy YES

(Evaluation Results for Examples and Comparative Examples)

Hereinafter, evaluation of test results for Examples and Comparative Examples shown in Tables 1 and 2 will be summarized.

(1) Pressure Resistance Strength at 100° C. 1) Examples 1, 2, 3, 5

The test bag was fully inflated in a spherical shape by feeding air, the easily openable seal part was peeled off after three seconds, and steam was properly released without bursting noise and leakage of contents (water). When the easily openable seal part was checked after the completion of the test, in Examples 1, 2, 3, the skin layer 5 was teared off, in Example 5, the bead part 7 was peeled off from the sealant layer 10 b of the seal part and the easily peelable layer 4 was agglomeration-peeled off.

That was a normal peeling situation. The three seconds mentioned above is the time that the test bag withstands without breaking-off.

2) Example 4

Although steam was properly released by peeling off of the easily peelable layer as in (1) 1), the time to steam releasing after inflation into a spherical shape was extended to five seconds. The evaluation in Table 1 will be mentioned in (2) 2) below.

3) Comparative Examples 1, 2

Steam was properly released as in (1) 1).

4) Comparative Example 3

Steam was not released even after the test bag was fully inflated into a spherical shape by feeding air but after eight to fifteen seconds, the test bag was burst with a large noise and water was leaked. When the test bag was checked after the completion of the test, the bag main body film was in a stretched state, and a central part of the bag upper surface film was largely teared off in the oblique direction. Further, the easily peelable seal part was not peeled off.

(2) Microwave Automatic Steam Releasing Property 1) Examples 1, 2, 3, 5

As Water in the test bag was boiled, the test bag was fully inflated in a spherical shape, then, the easily openable seal part was peeled off after two seconds and steam was properly released without bursting noise and leakage of contents (water). When the easily openable seal part was checked after the completion of the test, in Examples 1, 2, 3, the skin layer 5 was teared off, in Example 5, the bead part 7 was peeled off from the sealant layer 10 b of the seal part and the easily peelable layer 4 was agglomeration-peeled off, which was a proper peeling situation.

2) Example 4

Although steam was properly released as in (2) 1), the time to steam releasing after inflation into a spherical shape was extended to five seconds. Therefore, as described above, the example is regarded as slightly inferior to the other examples, thus is evaluated as “YES”—in the microwave automatic steam releasing property column in Table 1.

3) Comparative Examples 1, 2

Steam was properly released as in (2) 1).

4) Comparative Example 3

Steam was not released even after the test bag was fully inflated into a spherical shape but after eight to fifteen seconds, the test bag was burst with a large noise and water was leaked. When the test bag was checked after the completion of the test, the bag main body film was in a stretched state, and a central part of the bag upper surface film was largely teared off in the oblique direction. Further, the easily peelable seal part was not peeled off.

(3) Boil Sterilization Adequacy and Heating in Hot Water Adequacy 1) Examples 1, 2, 3, 4, 5

When the test bag was taken out and checked after the test, there was no break-off of the bag, the contents (water) were not leaked out, and the easily openable seal part and the other seal parts were not peeled off.

2) Comparative Examples 1, 2

When the test bag was taken out and checked after the test, there was break-off of the bag. The easily openable seal part was peeled off and the contents (water) were leaked out and lost.

4) Comparative Example 3

There was no break-off of the bag as in (3) 1).

CONCLUSION

Regarding the pressure release seal part 2 having the first seal mechanism 21 of the conditions shown as examples, from the view of the boil sterilization adequacy and the heating in hot water adequacy, based on Comparative Example 2, Examples 1 to 4, and Comparative Example 3 of Table 1, the thickness of the skin layer 5 is preferably 3 to 48 μm, in particular, based on Comparative Example 2 and Examples 1 to 3, the thickness of the skin layer 5 is more preferably 4 to 40 μm, further, based on Examples 1 to 3, the thickness of the skin layer 5 is further preferably 5 to 40 μm, and furthermore, best of all the thickness is most preferably 5 to 30 μm.

In addition to the viewpoint of the boil sterilization adequacy and the heating in hot water adequacy, the steam releasing property in microwave heating was added to the above viewpoint of, thus, the following conclusion was obtained.

That is, the pressure resistance strength at 100° C. is preferably 6 to 40 kPa based on Comparative Example 2, Examples 1 to 4, and Comparative Example 3 of Table 1, in particular, preferably 7 to 28.2 kPa based on Comparative Example 2 and Examples 1 to 4, and most preferably 8.6 to 9 kPa based on Examples 1 to 3.

The peak value of the seal strength at 100° C. is preferably 1.3 to 35 N/15 mm based on Comparative Example 2, Examples 1 to 4, and Comparative Example 3 of Table 1, in particular, more preferably 1.3 to 20 N/15 mm based on Comparative Example 2 and Examples 1 to 4, and furthermore preferably 1.5 to 17.1 N/15 mm. Among them, the thickness is most preferably 1.62 to 16.4 N/15 mm based on Examples 1 to 3.

Further, the peak value/intermediate value calculated by the peak of the seal strength at 100° C. and the intermediate value of Table 1 is preferably 1.3 to 3 based on Comparative Example 2 and Examples 1 to 4, in particular, more preferably 1.5 to 2.8, and among then, furthermore preferably 1.99 to 2.1 from Examples 1 to 3.

As described above, by employing the respective numerical value ranges of Table 1 as the entire pressure release seal part 2, the heating pouch that is able to compatible with microwave heating and the heating in hot water including boil heating can be provided.

From Table 2, by providing the bead part 7, the numerical values within the ranges of the respective strengths and the ratio of Table 1 can be employed as the entire pressure release seal part 2. Thus, it can be understood that there are no problems in the boil sterilization adequacy, the heating in hot water adequacy, and the steam releasing property in microwave heating.

DESCRIPTION OF REFERENCE NUMERALS

-   1: Heating pouch -   2: Pressure release seal part -   2 a: Front end (of pressure release seal part 2) -   3 a: Front end side (front connecting part) -   3 b: Back end side (back connecting part) -   3 c: Right end side (right connecting part) -   3 d: Left end side (left connecting part) -   3 e: Lateral seal (at the time of manufacturing pouch) -   4: Tape main body (easily peelable layer) -   5: Skin layer -   5 a: Tear (of skin layer 5) -   5 h: Peeling side skin layer -   5 n: Non-peeling side skin layer -   6: Flat part -   7: Bead part -   8: Steam port -   9: Base layer -   10: Bag sheet -   10 a: Base material -   10 b: Sealant layer -   10 h: Peeling off side sealant layer -   10 n: Non-peeling off side sealant layer -   11: Upper sheet part -   12: Lower sheet part -   13: Folding line (of plastic film 10 at the time of manufacturing     pouch) -   13 a: Ear part (of plastic film 10 at the time of manufacturing     pouch) -   16: Folded part (on left and right on bottom of gazette forming     plastic film 10 at the time of manufacturing pouch) -   14: First sheet member -   15: Second sheet member -   20: Easily peelable tape -   21: First seal mechanism -   22: Second seal mechanism -   d: Dancer roll -   f: Food product -   h: Run-over part -   J: Steam -   k: Housing space -   m: Seal surface -   s: Seal bar -   s0: Receiving base -   v: Left end side (of plastic film 10 at the time of manufacturing     pouch) -   w: Right end side (of plastic film 10 at the time of manufacturing     pouch) -   z1: Upstream (of manufacturing line) -   z2: Downstream (of manufacturing line) 

1. A heating pouch which is a bag sheet provided with an easily peelable seal part as a pressure release seal part, wherein the pressure release seal part adheres a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other, the pressure release seal part being peeled off at the time of an internal pressure rise so as to form a deaeration passage which communicates between the inside of the bag sheet and the outside of the bag sheet, the pressure release seal part being provided with an easily peelable layer and a skin layer, the skin layer being a resin layer constituting a seal surface that covers at least any one of the part of the sheet and the other part and which adheres to the remaining uncovered part, and the skin layer has higher seal strength at 100° C. than that of the easily peelable layer.
 2. A heating pouch which is a bag sheet provided with an easily peelable seal part as a pressure release seal part, wherein the pressure release seal part adheres a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other, the pressure release seal part being peeled off at the time of an internal pressure rise so as to form a deaeration passage which communicates between the inside of the bag sheet and the outside of the bag sheet, and the pressure release seal part is provided with a flat part and a bead part, the flat part serving as a flat seal surface and the bead part being formed as projecting toward the inner surface side of the bag sheet rather than the flat part.
 3. The heating pouch according to claim 1, wherein the heating pouch is used for both microwave heating and heating in hot water.
 4. A heating pouch which is a bag sheet provided with an easily peelable seal part as a pressure release seal part, wherein the pressure release seal part adheres a part of the sheet constituting the bag sheet to the other part of the sheet so as to overlap each other, the pressure release seal part being peeled off at the time of an internal pressure rise so as to form a deaeration passage which communicates between the inside of the bag sheet and the outside of the bag sheet, the pressure release seal part having a pressure resistance strength 6 to 30 kPa at 100° C., wherein the heating pouch comprises the pressure release seal part provided with at least any one of a first seal mechanism and a second seal mechanism, and is capable of heating in hot water and by the microwave, the first seal mechanism provided with an easily peelable layer and a skin layer, the skin layer being a resin layer constituting a seal surface that covers at least any one of the part of the sheet and the other part which adheres to the remaining uncovered part, and the second seal mechanism is provided with a flat part and a bead part, the flat part serving as a flat seal surface and the bead part being formed as projecting toward the inner surface side of the bag sheet rather than the flat part, the bead part having higher pressure resistance strength than that of the flat part.
 5. The heating pouch according to claim 1, wherein the pressure release seal part is provided with an easily peelable tape, the easily peelable tape being more easily peelable at a temperature higher than a room temperature than being peelable at a room temperature.
 6. The heating pouch according to claim 1, wherein at least any one of a part of the sheet constituting the bag sheet and the other part of the sheet constituting the bag sheet comprises an easily peelable layer.
 7. The heating pouch according to claim 6, wherein the pressure release seal part is not provided with a tape having the easily peelable layer but the sheet constituting the bag sheet itself is provided with the easily peelable layer.
 8. The heating pouch according to claim 1, wherein the skin layer is to be 3 to 40 μm thick.
 9. The heating pouch according to claim 2, wherein the heating pouch is used for both microwave heating and heating in hot water.
 10. The heating pouch according to claim 2, wherein the pressure release seal part is provided with an easily peelable tape, the easily peelable tape being more easily peelable at a temperature higher than a room temperature than being peelable at a room temperature.
 11. The heating pouch according to claim 3, wherein the pressure release seal part is provided with an easily peelable tape, the easily peelable tape being more easily peelable at a temperature higher than a room temperature than being peelable at a room temperature.
 12. The heating pouch according to claim 4, wherein the pressure release seal part is provided with an easily peelable tape, the easily peelable tape being more easily peelable at a temperature higher than a room temperature than being peelable at a room temperature.
 13. The heating pouch according to claim 2, wherein at least any one of a part of the sheet constituting the bag sheet and the other part of the sheet constituting the bag sheet comprises an easily peelable layer.
 14. The heating pouch according to claim 3, wherein at least any one of a part of the sheet constituting the bag sheet and the other part of the sheet constituting the bag sheet comprises an easily peelable layer.
 15. The heating pouch according to claim 4, wherein at least any one of a part of the sheet constituting the bag sheet and the other part of the sheet constituting the bag sheet comprises an easily peelable layer.
 16. The heating pouch according to claim 3, wherein the skin layer is to be 3 to 40 μm thick. 